> De: "Brian Goetz" <brian.go...@oracle.com> > À: "Kevin Bourrillion" <kev...@google.com>, "Guy Steele" > <guy.ste...@oracle.com> > Cc: "amber-spec-experts" <amber-spec-experts@openjdk.java.net> > Envoyé: Jeudi 10 Mai 2018 22:04:15 > Objet: Re: Treatment of nested 'break'
> This might not help, but perhaps think of it as a compound keyword; "break > switch" is not "break with an argument of switch", but a multi-word keyword > itself. > (Back in lambda, when we explored the consequence of using "return" in lambda, > and observed it foreclosed on nonlocal return should we ever want to get > there, > we briefly discussed "long return" as a compound keyword for that case. Same > game.) > Personally if I saw "break while", I think I'd immediately know what that > means, > and might even thank the author for being clear. You can also use any other word instead of break or break switch. By example, breakswitch 3; Rémi > On 5/10/2018 3:57 PM, Kevin Bourrillion wrote: >> I'm just going to say that naming a keyword as the argument of another >> keyword >> seems novel and unprecedented for Java, and as such I think should require >> pretty strong justification. >> On Thu, May 10, 2018 at 12:12 PM, Guy Steele < [ >> mailto:guy.ste...@oracle.com | >> guy.ste...@oracle.com ] > wrote: >>>> On May 10, 2018, at 3:06 PM, Brian Goetz < [ mailto:brian.go...@oracle.com >>>> | >>> > brian.go...@oracle.com ] > wrote: >>>>> I think these are both valid explanations, with different outcomes, but >>>>> anyway >>>>> it's fair to say that it would be confusing to have the latter >>>>> perspective and >>> >> then try to explain how a value break can get past a surrounding 'for' >>> >> loop. >>>> One option is: you can't. While I agree there is code that one might like >>>> to >>>> write that is made cumbersome by this, it's a valid option, and not one >>>> that is >>> > utterly terrible. >>>> Another option is to extend the break syntax along the lines of the >>>> proposed >>>> continue syntax. Suppose for every continuable construct x (for, while, >>>> switch) >>>> we supported "continue x". So for every breakable construct y we could >>>> support >>>> "break y". If a for loop were enclosed in an expression switch, you could >>>> then >>> > say "break switch e". Then >>> > if (foo) >>> > break; >>> > else >>> > break 3; >>> > becomes >>> > if (foo) >>> > break for; >>> > else >>> > break switch 3; >>> > and it is much more obvious what is going on. >>> If we are willing to pile up keywords in that manner, an alternate >>> possibility >>> is to spell a value-returning break in a different way: >>> return switch <expression>; >>> Then your example can become (I have added the implicit context): >>> switch (…) { case 17 -> { >>> … >>> for (…) { >>> ... >>> if (foo) >>> break; >>> else >>> return switch 3; >>> … } >>> … } >>> … } >>> The additional advantage of this approach is that it completely eliminates >>> the >>> syntactic ambiguity between >>> break variableName; >>> and >>> break labelName; >>> Given that we think most occurrences of “return switch” (or “switch return”, >>> take your pick) will be abbreviated by -> anyway, this might be an >>> acceptable >>> approach. >>> You can then still choose to go ahead and also allow things like >>> break for; >>> break switch; >>> break while; >>> continue for; >>> continue switch; >>> but that can be a separate decision; these become simply a way to avoid >>> using >>> statement labels. >>> —Guy >> -- >> Kevin Bourrillion | Java Librarian | Google, Inc. | [ >> mailto:kev...@google.com | >> kev...@google.com ]
